1. Technical Field
The present invention generally relates to footwear, and more specifically relates to structures for supporting a footwear.
2. Related Art
A common objective for most types of footwear designs is to address at least one of the following three biomechanical issues: shock attenuation, stability, and support. Shock attenuation involves the absorption of shock, shock diffusion and pressure distribution. The ability of a footwear to attenuate shock forces can greatly reduce the pain and discomfort to a user of the footwear for any given application. Shock absorption may be addressed by the type of materials that are used in the footwear. Various types of materials have excellent shock absorption properties, especially for the thin layers that are typically required for a footwear. Shock diffusion relates to dampening of shock forces to reduce how much of the shock force is transferred to the user. Again, the type of material as well as the structure of the footwear may significantly affect shock diffusion by a footwear. Pressure distribution relates to the distribution or spreading out of a point force or pressure point such as, for example, a heel strike pressure point at the heel of a footwear when walking or running. Pressure distribution is often accomplished using a plate-like structure wherein the amount of pressure distribution is controlled by the type and thickness of the plate material.
The stability of a footwear is a another important biomechanical issue and may be controlled by the material properties and structure of various features of a footwear. For example, a footwear with a very thick sole that raises an individual's center of gravity beyond a natural position may provide a very unstable scenario. Further, some types of materials used in footwear are very flexible and if used alone without any other support features may create an unstable footwear. Some types of material that do not allow flexibility may effect the natural motion of the foot and further create instability.
The support provided by a footwear is also important. A common objective for a footwear is to obstruct as little as possible the natural movements of the foot while supporting the foot where it is necessary for a given footwear application. In some applications such as sports like soccer and tennis, lateral support is extremely important, while arch support and support along the longitudinal axis of the footwear may be a greater consideration for applications such as running and walking. Other applications that require standing for long periods of time may require the type of support which reduces the amount of work the users foot muscles must exert in order to maintain proper posture and balance while standing.
A further biomechanical consideration for footwear is the flexibility of the forefoot, midfoot and hindfoot portions of the footwear. A natural motion of the foot requires significant flexing and bending in a longitudinal direction as well as some complex lateral and torsional motion. While some types of inflexibility may be important for certain performance enhancement objectives, most footwear applications require a range of flexibility in each major section of the footwear. For example, undue amounts of torsional flexibility about a transverse axis of the footwear in the area of the arch of the foot may result in inadequate guiding and holding of the foot if the footwear bottom also provides too much longitudinal flexibility in that region of the footwear.
One known attempt at an “all day comfort” footwear that addresses shock attenuation, stability, support and flexibility includes a firm lasting insole that is layered in the footwear just above the midsole and extends along the hind of the footwear up to the midfoot of the footwear. This plate-like structure provides support and diffuses forces in the heel. In an effort to attenuate shock forces, the footwear may include a gel or other type of insert material at the outsole or within the midsole of the footwear. Although the plate structure may distribute pressure, the heel strike and other significant shock forces are not dissipated very well. Furthermore, because there is no support structure in the forefoot of the footwear, the footwear may be entirely too flexible for a given application and fails to provide the torsional rigidity that is necessary for support and stability of the footwear.
Another known footwear design that attempts to address the biomechanical issues described above includes a sole structure that has multiple horizontal and/or vertical layers of foam materials that each have different properties. The outsole may also include certain structures that provide some lateral support. This type of design is difficult to alter for the support, stability and shock attenuation needs of different applications while concurrently providing necessary flexibility along the length of the footwear.
The cost and feasibility of a footwear design is a further consideration when designing a footwear that addresses the above-mentioned biomechanical issues. Some footwear designs may include materials or structures that are not conducive to cost effective manufacturing and assembly of the footwear.